A large number of methods and apparatus are known for removing oily and floating waste (which in the following disclosure will be simply designated in general as "oil") from the surface of bodies of water, and in particular from the surface of the sea, of lakes and rivers. For exemplary purposes, reference if made to the method and apparatus described in GB-A-1 206 794, DE-A-2 931 795 and U.S. Pat. Nos. 4,119,541 and 3,684,095. However, said methods and apparatus already known in the art, have considerable drawbacks, and particularly the following:
a) a very low collecting efficiency, further remarkably reduced if an even slight wave motion is present;
b) the oily floating waste is obliged, since already the first step of the process, to pass through a level drop from the sheet of water containing the floating matter to be removed, to the fluid surface within the apparatus performing the process (see U.S. Pat. No. 4,119,541). As a consequence emulsifying and stirring actions are produced between oily matter and water, being previously perfectly separate, one floating over the other, and the effects of these actions have to be subsequently reduced or counteracted thus negatively affecting the efficiency and adding to the structural complexity of the apparatus. For example according to the above-mentioned U.S. patent it is necessary not only to provide anti-emulsion plates 5, 5a, but also to cause water running zigzag with a longer path and to adopt both baffles 14 for maintaining a quiescent region and densitometers for detecting a possible content of oil carried by water beyond the filter. In order to improve separation and stratification of oily matter from water an array of the above-mentioned plates 5, 5a is used, the plates being parallel, slanting suitably spaced apart and provided with tiny holes;
c) those methods and related apparatus based on the principle of enrichment in oil of the floating matter with water being discharged from the bottom and the concentrated oil recovered at the upper layers, such as in U.S. Pat. Nos. 4,119,541 and 3,684,095, require a very complex instrumentation system to control the level differences with respect to the outside, thickness of the concentrated oily layer and percentage of oil in the discharged water. Furthermore these instrumentation systems show some problems in their setup for operating in a smooth body of water and even cannot be used at all when such a body of water becomes slightly rough;
d) all these known processes accomplish their effect in a single operative step, not to be repeated, by subjecting all the fluid under treatment to only one type of process without dividing it into successive steps, each relating to a different physical treatment specifically required to that particular step of the process, thus resulting in a low operational flexibility of the overall process. Therefore the known apparatus only seldom perform in the best operating conditions; e) remarkable transportation problems due to the large size of the apparatus, when they have to work in an even slightly rough sea, and the fact that they cannot be easily disassembled in order to make their transportation easier;
f) a high operation complexity which makes absolutely compulsory a continuous attendance on board of personnel whose safety often puts a constraint to the use of such apparatus, which are further burdened by the logistics of said personnel;
g) unsatisfactory seaworthiness as far as maneuvering and wave motion resistance, especially at sea, even when only slightly rough.
It is an object of the present invention to provide a method and an apparatus for removing oily and in general floating waste matter from bodies of water, which overcome the above-mentioned drawbacks known in the art.
One of the basic features of the present invention resides in the fact that the oily matter floating on the water is concentrated and at the same time separated from the greatest quantity of water as possible still before having to flow through any passage or level drop device which may cause therein some emulsifying and/or stirring action.
Another basic feature of the present invention is that, contrary to the prior art according to which a single, simple process is applied to all the fluid under treatment (see point d) above), a complex process is applied consisting in a combination of various processes, each of which forms systematically part of the global one, is dimensioned according to the quantity of fluid to be treated and is provided with the required auxiliary equipments which are specifically required.
A further basic feature of this invention is the fact oily matter removal may be performed with a constantly high separating efficiency, even in rough sea conditions, and by means of an apparatus whose weight and dimensions are relatively limited, at least compared to similar apparatus already known in the art. That is possible owing to the fact that, on the one hand the collection of the whole amount of oil involved is guaranteed, and on the other hand the amount of water subjected with the oil to the process is the least possible. A further important aspect of this invention, which improves the oil removal efficiency, is the fact that the various phases of preliminary separation and surface concentration of the oil are performed not only without resorting to the use of differential levels or other situations which could produce stirring and/or emulsifying in the liquid body, but also providing mechanical means for setting in motion the various liquid flows to be passed through by these flows only downstream of their final separation, and means adapted to reduce the effect of the turbulence induced by the wave motion on the liquid flows being treated, in addition to special design features and devices.
A further feature of this invention is the possibility to be readily disassembled in order to make it easily transportable along roads, and then assembled again near the usage location.
Still according to this invention, the process is such that it can be followed through automatic and/or radio-controls to the operating components of the apparatus wherein it is performed, whereby continuous attendance of personnel on board may not be required. In this way it has been made possible, on the one hand to provide the apparatus with qualities of further reduced weight, and on the other hand to enable the apparatus to be used in very rough sea conditions, when the apparatus already known would not be able to operate for personnel safety reasons.
A further feature of this invention is the fact that the oil transfer operation to the stocking facilities can be performed simultaneously to the forward motion of the apparatus, or while the latter is at a standstill, without having to interrupt the collecting operations.
A further particular advantage of this invention relative to the state of the art resides in the possibility to adjust the plurality of operating parameters to the variable conditions associated with each particular pollution reducing operation, such as the roughness of the sea, the density and thickness of the oil layer, the removal velocity, the allowable residual pollution, and so on, in order to attain an optimum operation flexibility. Finally, the apparatus is highly seaworthy, in terms of ability to maneuver and of sea resistance.
The method according to the present invention is characterized by the features recited in claim 1 and the apparatus for putting in practice the same is characterized according to claim 8.